This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-086382, filed Mar. 27, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a polishing pad, polishing apparatus and polishing method, more specifically, to a polishing pad, polishing apparatus and polishing method suitable for manufacturing a semiconductor device.
Recently, with the tendency of integration and miniaturization of semiconductor devices in the field of manufacturing semiconductor devices, various micro-processing techniques have been developed. Of them, chemical mechanical polishing (CMP) is an essential technique for forming a planarized interlayer insulating film, plug, buried metal wiring and buried isolation.
However, the CMP techniques have a problem. It is necessary to determine the end point of the CMP (at which point the CMP is stopped). Usually, the end point is detected by monitoring the friction force between the surface of a semiconductor wafer and a polishing pad during the polishing. The friction force is monitored by measuring the current of a motor rotating a polishing table or a polishing head. The end point is determined based on a change in measurement value of the current. However, in some cases, depending upon the polishing conditions or the structure of a surface to be polished (polish-receiving surface), the friction force does not change significantly. Particularly when the polishing is performed while a lightweight is applied, the friction force rarely changes.
There is another end-point detection method, in which the end point is optically monitored. In this method, the thickness of the surface film of a semiconductor wafer under polishing is optically measured, and the change of the film type is detected based on a reflection rate of the surface of the wafer. However, this method entails technical difficulties. Light must be applied by some means to the wafer surface under polishing.
To overcome the aforementioned problems, U.S. Pat. No. 4,793,895 proposes a method for monitoring current flowing on a polish-receiving surface, by a conductive electrode formed on a polishing pad. However, this method has problems. The conductive electrode exposed in the surface of the polishing pad is susceptible to corrosion with a polishing solution. In addition, the exposed surface of the conductive electrode may adversely affect the polishing characteristics of CMP. In short, the material for the electrode is limited by the use of the conductive electrode. It is actually difficult to select the material having no adverse effect upon the polishing characteristics.
As described above, how to detect the end-point is one of the problems associated with the CMP technique. However, conventional end-point detection methods do not always solve this problem.
An object of the present invention is to provide a polishing pad, a polishing apparatus, and a polishing method capable of easily and accurately determining an end point of polishing such as CMP.
According to a first aspect of the present invention, there is provided a polishing pad for use in polishing a surface of a substrate; comprising: a pad main body having a polishing surface; and a plurality of electrode portions formed in the pad main body and mutually spaced apart in a plane direction of the pad main body, each of the electrode portions being formed of an conductive portion and an insulating portion formed on the conductive portion.
According to a second aspect of the present invention, there is provide a polishing apparatus for polishing a surface of a substrate by attaching the polishing pad thereto, comprising: a polishing table to which the polishing pad is to be attached; a holding portion for holding the substrate such that the surface of the substrate is in contact with the polishing surface and a surface of the insulating portion of the polishing pad attached to the polishing table; a driving portion for moving the polishing table and the holding portion relative to each other; a polishing liquid supply portion for supplying a polishing liquid onto a surface of the polishing pad attached to the polishing table; a voltage application portion for applying an alternating voltage between the electrode portions of the polishing pad attached to the polishing table, whereby a current flows along the surface of the substrate held by the holding portion; and a detecting portion for detecting the current via the electrode portions of the polishing pad attached to the polishing table.
According to a third aspect of the present invention, there is provide a polishing apparatus for polishing a surface of a substrate by attaching a polishing pad; comprising: a polishing table to which the polishing pad having a plurality of holes is to be attached, the polishing table including a polishing-table main body having a main surface and a plurality of electrode portions formed in the polishing-table main body and mutually spaced apart in a plane direction of the polishing-table main body, each of the electrode portions being formed of a conductive portion and an insulating portion formed on the conductive portion, each of the electrode portions having a protruding portion protruding from a plane including the main surface, the protruding portion being capable of fitting into the corresponding hole formed in the polishing pad; a holding portion for holding the substrate such that the surface of the substrate is in contact with a polishing surface of the polishing pad attached to the polishing table and a surface of the insulating portion of the polishing table; a driving portion for moving the polishing table and the holding portion relative to each other; a polishing liquid supply portion for supplying a polishing liquid onto a surface of the polishing pad attached to the polishing table; a voltage application portion for applying an alternating voltage between the electrode portions, whereby a current flows along the surface of the substrate held by the holding portion; and a detecting portion for detecting the current via the electrode portions.
According to a fourth aspect of the present invention, there is provide a polishing apparatus for polishing a surface of a substrate, comprising: a polishing table including a polishing-table main body having a polishing surface and a plurality of electrode portions formed in the polishing-table main body and mutually spaced apart in a plane direction of the polishing-table main body, each of the electrode portions being formed of a conductive portion and an insulating portion formed on the conductive portion, a holding portion for holding the substrate such that the surface of the substrate is in contact with the polishing surface and a surface of the insulating portion of the polishing table; a driving portion for moving the polishing table and the holding portion relative to each other; a polishing liquid supply portion for supplying a polishing liquid onto the polishing surface of the polishing table; a voltage application portion for applying an alternating voltage between the electrode portions, whereby a current flows along the surface of the substrate held by the holding portion; and a detecting portion for detecting the current via the electrode portions.
According to the present invention, it is possible to effectively detect the end point of polishing in a polishing process of a conductive film (any film such as semiconductor films e.g., polysilicon film, other than metal films may be used as long as it has a conductivity) on the surface of a substrate. More specifically, the end point of polishing can be easily and accurately determined by detecting the conductivity of the substrate surface by means of a plurality of electrode portions. As a result, the polishing is neither insufficient nor excessive and appropriately performed.
The conductive portion is protected by the insulating portion. Therefore, even if a polishing solution having a strong corrosion property is used, the conductive portion is not corroded. The current is detected by applying a high-frequency alternating voltage between the electrode portions and by functioning the insulating portion as a capacitor. Since the conductive portion is not directly exposed to the polishing solution and the high-frequency alternating voltage is applied, it is possible to prevent electrolysis of the polishing solution. Furthermore, the insulating portion may be formed of a material chosen from various insulating materials. Therefore, the insulating portion may be formed of the same or analogous material to that of the polishing pad. As a result, it is successfully prevent the electrode portion from adversely affecting the polishing properties.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.